Wei Wang1, Wei Li1, Xueqian Shang1, and Xiaoying Wang1
1Peking University First Hospital, Beijing, China, People's Republic of
Synopsis
The
study preliminary compared the ability of non-contrast-enhanced MRI and
contrast-enhanced CT in detection, characterization and staging of esophageal
cancer. Ten patients’ chest CT and MR images were
subjectively evaluated. We found that MR was not inferior to CT, and showed
superior capacity in detecting early unapparent cancer, delineating the tumor
precisely and depicting perfect contrast of surrounding structures. Also MR was
relatively safe than contrast-enhanced CT. MR may be a potential useful tool
for evaluation esophageal cancer. Purpose
The purpose of the study
was to compare non-contrast-enhanced MRI and contrast-enhanced CT for pretreatment evaluation of esophageal cancer.
Methods
Ten
patients with biopsy-proven esophageal cancer underwent pretreatment contrast-enhanced
chest CT and unenhanced chest MRI at 3.0T. Axial FSE T2WI and DWI with respiratory triggering were scanned
using a 32-tunnel body phased-array coil. The parameters for T2WI: TR/TE=8000-10000/80ms,
FOV=36cm, including supraclavicular fossa to upper abdomen, matrix=384×384，NEX=2.5, slice thickness/spacing=5mm/1mm. The parameters
for DWI: b value=800s/mm
2, TR/TE=8000-10000/50-80ms, FOV=36cm, including
supraclavicular fossa to the upper abdomen, matrix 128×128，NEX=1, slice thickness/spacing=5mm/1mm.
The detection, characterization and staging of esophageal tumors were compared subjectively between CT and MR images.
Results
All
the patients’ cancer can be detected by both CT and MRI, but for the tumor seen
as an asymmetric mild thickening of esophageal wall, it is not easy to detect
by CT(4/10, early stage). MRI has greater diagnostic confidence than CT because
DWI sequence showed high signal intensity of tumor(10/10) which increase the
sensitivity of detection.
The esophageal cancer showed similar morphological
features on CT and MR including wall thickening(7), mass(1) and ulcer(2). On
contrast-enhanced CT images, the tumor had mild enhancement (Median, range:
15HU, 7-24HU) without clear tumor boundary. Combining T2WI and DWI, MRI images could show
clear upper and lower bounds of tumor for all patients. On T2WI, the tumors
were intermediate to high signal intensity and the layer of esophageal wall
could be demonstrated distinctly on some slices.
Seven patients obtained the same tumor stage
for CT and MR(three T1-2, three T3 and one T4), and for the other three, CT was
over-staged than MRI: two T4(T3) and one T3(T1-2) on CT(MRI). The periesophageal fat and mediastinal structure
could be seen clearly at MRI. Although
the fat planes between the esophageal mass and adjacent structures was
obliterative on CT, but the intact wall of adjacent tissue such as aorta, trachea,
left atrium can be recognized on MRI.
Discussion
MRI
of esophagus is often considered technically challenging, such as organ motion
and flow artifacts. Also, the central location of mediastinum is associated
with reduced receiver coil sensitivity. These years, with the improvement of
MRI techniques, it enabled proper visualization of esophagus using MRI1.
A proper MRI protocol should consist of both
T2WI and DWI sequences. The T2WI images may enable depiction of different
layers of esophageal wall and provide excellent contrast between esophagus and
its surrounding structures2. The DWI, a functional sequence, assesses the
diffusion of water molecules within different tissues. The esophageal caner
demonstrates increased signal intensity on DWI, and improved the sensitivity to
detect the tumor and the confidence for diagnosis.
Esophageal cancer is the eighth most
frequently diagnosed cancer worldwide3. Accurate pretreatment
staging of esophageal cancer is integral for assessing and determining a
suitable treatment plan. Routine non-invasive local staging of esophageal
cancer relies on CT. However, due to the lack of soft tissue contrast the
individual layers of the esophageal wall cannot be recognized and delineation of
the tumor is not possible as it is of similar attenuation to the normal
esophageal wall, even using the contrast medium. Therefore, CT is of limited
value for locoreginal tumor staging4. According to the results
above, MRI could detect esophageal cancers similar to CT, and displayed
superior ability in detecting early tumors that may not be obvious on CT.
The delineation of lesion was demonstrated clearer on MR than CT. The tumors
may be over-staged by CT, due to the periesophageal fat planes could be seen
clearly at MRI that may not be depicted at CT. Furthermore; MRI is relatively
safe than contrast-enhanced CT without the risks of radiation and contrast medium.
Conclusion
Unenhanced
MRI was similar and somewhat superior to CT in detection, characterization and staging of
esophageal cancer and without risks of radiation and contrast medium. Although
MRI plays no role in current routine guidelines of esophageal cancer, it has the potential to act as
a new non-invasive tool in the near future.
Acknowledgements
I would like to show my gratitude to doctor Xueqian Shang of Thoracic surgery and MR technologist Wei Li. References
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